Electron discharge device



P. L. SPENCER ELECTRON DISCHARGE DEVICE Filed July 18, 1945 OUTPUT 2Sheets-Sheet l AWN/rm.

FHFOV l. S y/05 P. L. SPENCER ELECTRON DISCHARGE DEVICE Feb, 7 195@ 2Sheets-Sheet 2 Filed July l8, 1945 Patented Feb. 7, 1950 ELECTRONDISCHARGE DEVICE Percy L. Spencer, West Newton, Mass., assignor toRaytheon Manufacturing Company, Newton, Mass., a corporation of DelawareApplication July 18, 1945, Serial No. 605,755

3 Claims (01. 250-275) My present invention relates toelectron-discharge devices, and more particularly to electrondischargedevices of the so-called magnetron type, which are adapted to generateelectrical oscillations having wave lengths of the order of a fewcentimeters, or less.

It is difficult to obtain appreciable power from magnetrons operating atthe very short wave lengths above referred to because of the sizetowhich said wave lengths necessarily limit the anode structures thereof.Furthermore, such magnetrons can be tuned only over relatively narrowbandwidths.

It is, therefore, one of the objects of my present invention to soconstruct a magnetron that, notwithstanding the very short wave lengthat which it is intended to operate, appreciable power may be obtainedtherefrom.

It is another object of my present invention to so construct saidmagnetron that the frequency of the oscillations generated thereby maybe varied over an appreciable range.

These, and other objects of my present invention, which will become moreapparent as the detailed description thereof progresses, are attained,briefly, in the following manner:

I provide the magnetron of my present invention with an anode structurewhich includes at least two groups of cavity resonators, eachdimensioned to oscillate at a different frequency, and all of saidfrequencies, preferably, bearing a harmonic relationship to each other.Said groups of cavity resonators are axially displaced with respect toeach other, preferably, along a centrallylocated cathode structure, andsaid groups of cavity resonators are, in addition, preferably, disposedat different distances from said cathode structure.

A magnetic field is established transversely of the electron-pathbetween said cathode and anode structures, said magnetic field beingvariable so that the orbital frequency of the electrons emitted by saidcathode structure may be adjusted so as to excite the above-mentioneddifferently-dimensioned cavity resonators simultaneously at any I thatby combining these oscillations, resultant oscillations are obtainedwhich contain appreciable power at the average of the constituentfrequencies, namely, at a frequency correspond-,- ing to a wave lengthof 7.5 cm. If the magnetic field is altered so that the orbitalfrequency of the electrons emitted by the cathode structure is such thatthe group of l0-cm. cavity resonators oscillates more strongly than .theother group, the frequency of the combined oscillations increases, andvice versa. I have further found that by the means described, I canobtain appreciable power at any frequency between the frequenciescorresponding to the dimensions of the diiferent groups of said cavityresonators.

In the accompanying specifications I shall describe, and in the annexeddrawings show, an illustrative embodiment of the electron-dischargedevice of my present invention. It is, however, to be clearly understoodthat I do not wish to be limited to the details herein shown anddescribed for purposes of illustration only, inasmuch as changes thereinmay be made without the exercise of invention and within the true spiritand scope of the claims hereto appended.

In said drawings,

Fig. 1 is a vertical sectional view taken substantially through thecenter of an electrondischarge device made in accordance with theprinciples of my present invention; and

Fig. 2 is a fragmentary, perspective view taken substantially at thesame line as Fig. 1.

Referring now more in detail to the aforesaid illustrative embodiment ofmy present invention, and with particular reference to the drawingsillustrating the same, the numeral 5 generally designates anelectron-discharge device of the magnetron type. Said device includes acentrally-disposed cathode structure 6, an anode structure 1 surroundingsaid cathode structure, and means 8 for establishing a magnetic fieldtransversely of the electron-path between said cathode and anodestructures.

The anode structure 1, preferably, comprises a cylindrical body -9, madeof highly conductive material, such as copper, and provided with atleast two'axially displaced groups it and II of highly conductive,vertically aligned vanes 12 and I3, one of said groups, for example, thegroup I0, being radially disposed and extending inwardly from a boss l4formed on the interior surface of the body 9, and the other group,likewise, being radially disposed, but extending inwardly from theinterior surface, itself, of said body 9.

Each adjacent pair of the vanes l2 and I3 of each of the groups therefconstitutes, together with that portion of the cylindrical body 9 lyingtherebetween, a cavity resonator whose natural resonant frequency isdependent upon the inductance and capacitance built therein as afunction, primarily, of the physical dimensions of the elements makingup the same.

The vanes of one of the groups, here shown as the vanes I 2 of the group[0, are smaller than'the vanes of the other group, so that the cavityresonators formed by the first-mentioned group frequency correspondingto a wave length of 7.5

are resonant at a higher frequency .than thoseformed by the remaininggroup. For example,

the dimensions of the smaller cavity resonators may be such that theyhave a natural resonant frequency corresponding to a wave length of 5cm., while the dimensions of the remaining cavity resonators may be suchthat they resonate at a frequency corresponding to a wave length of cm.It is preferred that the smaller vanes extend to within a shorterdistance of the cathode structure 6 than do th'elarger vanes. Underthese conditions, it is possible, as will be hereinafter more fullydescribed, to obtainappreciable power at any frequency corresponding toany wave length between 5 and 10 cm.

It is preferred, althoughnot necessary, that the alternate vanes of bothgroups l0 and II thereof be electrically interconnected, for example, byconducting straps I5 to 22, inclusive, in order to suppress spuriousoscillations at undesired frequencies.

The cathode structure 6, preferably, comprises a cathode sleeve 23 made,for example, of nickel, and provided with a highly electron-emissivecoating 24, of the well-known alkaline-earth metal oxide type. Thesleeve 23 is provided with heating filament, not shown, having terminals25 and 26 connected to lead-in conductors 21 and 28 which enter thedevice through lass seals, not shown, at the ends of pipes 29 and 30threadeclly engaged and hermetically sealed-into the cylindrical body 9,said lead-in conductors being connected to a suitable source of filamentvoltage.

The cylindrical body 9 is closed at its ends by plates 3| and 32, thejunctions between said plates and said body being hermetically sealed.The plates are provided with central apertures 3.1 and 34 to receivestepped portions of pole pieces 35 and 36, the latter being providedwith windings 31 and 38 connected in series with each other and with anadjustable-source v39 of unidirectional voltage, for example, a battery40 having a potentiometer 4| across the same.

When a device such as has been described is provided with a suitablevoltage between its cathode and anode structures, and the magnitude ofthe magnetic field, which is transverse of the electron-path betweensaid cathode and anode structures, is appropriately adjusted, the cavityresonators formed by the groups In and l I of-the vanes l2 and i3 willhave electrical-oscillations generated therein. At a certain, what Ishall call, intermediate value of magnetic field, both groups of cavityresonators will be equally excited. At a higher value of magnetic field,the oscillations will be stronger in the cavity resonators nearer to thecathode structure, in this case, those formed by the group "of vanes l2.At a lower value of magnetic field, the other group of cavity resonatorswill have the stronger oscillations generated therein.

Now, power may be extracted from the device by means of a loop 42 whichmay enter the device through a pipe 43, the loop being so disposed cm.,and thepower at this frequency can be picked out by applying the outputof the device to a properly tuned circuit 44.

-' n power at a higher frequency is desired, the

magnitude of the magnetic field may be increased by adjusting the sourceof voltage 39 to favor oscillation in the shorter wave length cavityresonators, and correspondingly retuning the circuit 44.

Finally, if poweriat a lower frequency is desired, the magnitude of themagnetic field may be reduced so that oscillation will be favored in thelonger wave length cavity resonators, and again, correspondingly tuningthe circuit 44.

This completes the description of the aforesaid illustrative embodimentof my present invention.

It will be noted from all of the foregoing that Ihave provided amagnetron which is so constructed that appreciable power can be obtainedtherefrom notwithstanding the very short wave length at which it isintended to operate. It will further be noted that merely by alteringthe magnitude of the magnetic field of said magnetron I am enabled toobtain said power at any frequency within a band of considerable width.

Other objects and advantages of my present invention will readily occurto those skilled in the art to which the same relates.

What is claimed is:

1. An electron-discharge device comprising: a cathode; an anodestructure, spaced from said cathode, and incorporating a plurality ofgroups of differently dimensioned cavity resonators; the entrances tothe cavity resonators of each of said groups of cavity resonators beingdisposed at different distances from said cathode; adjustable means,adjacent said cavity resonators, for establishing a magnetic field ofvariable magnitude transversely of the electron path between saidcathode and anode structure; and output means coupled in common with allof said groups of cavity resonators.

2. An electron-discharge device comprising: a a cathode; an anodestructure, spaced from said cathode, and incorporating a plurality ofgroups of differently dimensioned cavity resonators; said groups ofcavity resonators being axially displaced along the length of saidcathode and the entrances to the cavity resonators of each of saidgroups thereof being disposed at different distances from said cathode;adjustable means, adjacent said cavity resonators, for establishing amagnetic field of variable magnitude transversely of the electron pathbetween said cathode and anode structure; and output means coupled incommon with all of said groups of cavity resonators.

3. An electron-discharge device comprising: a cathode; an anodestructure, spaced from said cathode, and incorporating a plurality ofgroups of differently dimensioned cavity resonators; each group of saidcavity resonators including a plurality of inwardly-directed,radially-disposed anode vanes each adjacent pair of which, together withthat portion of said anode structure lying therebetween, constitute oneof said cavity resonators; said groups of cavity resonators beingaxially displaced along the length of said cathode, and the inner endsof the anode vanes of each group terminating at a different distancefrom said cathode; adjustable means, adjacent said cavity resonators,for establishing a magnetic field of variable magnitude transversely ofthe electron path between said cathode and anode structure; and outputmeans coupled in common with all of said groups of cavity resonators.

PERCY L. SPENCER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,114,114 Roberts Apr. 12, 19382,250,698 Berline July 29, 1941 2,295,315 Wolfi Sept. 8, 1942 2,402,983Brown July 2, 1946 2,404,212 Bondley July 16, 1946 2,414,085 HartmanJan. 14, 1947 2,419,172 Smith Apr. 15, 1947 15 2,423,161 Spencer July 1,1947

